Bigtable

A Distributed Storage System for Structured Data

Bigtable is a distributed storage system (built by Google) for managing structured data that is designed to scale to a very large size: petabytes of data across thousands of commodity servers.

Some features

• fast and extremely large-scale DBMS
• a sparse, distributed multi-dimensional sorted map, sharing characteristics of both row-oriented and column-oriented databases.
• designed to scale into the petabyte range
• it works across hundreds or thousands of machines
• it is easy to add more machines to the system and automatically start taking advantage of those resources without any reconfiguration
• each table has multiple dimensions (one of which is a field for time, allowing versioning)
• tables are optimized for GFS (Google File System) by being split into multiple tablets – segments of the table as split along a row chosen such that the tablet will be ~200 megabytes in size.

Architecture

BigTable is not a relational database. It does not support joins nor does it support rich SQL-like queries. Each table is a multidimensional sparse map. Tables consist of rows and columns, and each cell has a time stamp. There can be multiple versions of a cell with different time stamps. The time stamp allows for operations such as “select ‘n’ versions of this Web page” or “delete cells that are older than a specific date/time.”